The present invention relates to a diagnostic reagent for detecting hepatitis C virus (HCV) infection by utilizing immunoagglutination.
In regard to hepatitis C, HCV gene was detected by the research group of Chiron Corporation, U.S.A., in 1988 prior to the detection of HCV. To detect antibodies to HCV, various recombinant antigens or synthetic peptides have been investigated, and kits for detecting HCV-associated antibodies have been developed. The methods of detection now available are agar diffusion, counterimmunoelectrophoresis, radioimmunoassay, enzyme immunoassay, passive hemagglutination, and latex agglutination.
Known HCV antigen proteins for use in the detection of HCV-associated antibodies are core and envelope proteins as structural region proteins, and NS1 to NS5 proteins as non-structural region proteins. One HCV antigen protein alone is not sufficiently high in detection sensitivity, and is also problematical in specificity. Thus, a suitable combination of proteins in structural and non-structural regions is used (Proc. Natl. Acad. Sci. USA 89:10011-10015, 1992). Attempts to increase the detection sensitivity further are also made. With the particle agglutination method, for example, the number of HCV antigens for sensitization of particles is increased, or polypeptide having HCV antigenic activity is heat-treated (Japanese Laid-Open Patent Publication No. 1002273/94); alternatively, a fusion protein constructed from HCV antigen protein and carrier protein is coated onto hydrophilic particles for their sensitization (Japanese Laid-Open Patent Publication No. 198723/95).
The use of synthetic peptide as an antigen has also been attempted, but this use is generally said to lower the detection sensitivity.
Thus, there is a growing demand for a diagnostic reagent and a method of diagnosis which enable many samples to be measured with high sensitivity and rapidity.